/*
 * Latke - 一款以 JSON 为主的 Java Web 框架
 * Copyright (c) 2009-present, b3log.org
 *
 * Latke is licensed under Mulan PSL v2.
 * You can use this software according to the terms and conditions of the Mulan PSL v2.
 * You may obtain a copy of Mulan PSL v2 at:
 *         http://license.coscl.org.cn/MulanPSL2
 * THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO NON-INFRINGEMENT, MERCHANTABILITY OR FIT FOR A PARTICULAR PURPOSE.
 * See the Mulan PSL v2 for more details.
 */
package org.b3log.latke.util;

import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

/**
 * Id utilities.
 *
 * @author <a href="http://88250.b3log.org">Liang Ding</a>
 * @version 1.0.0.3, Sep 29, 2011
 */
public final class Ids {

    /**
     * Lock for unique id generation.
     */
    private static final Lock ID_GEN_LOCK = new ReentrantLock();

    /**
     * Sleep millisecond.
     */
    private static final long ID_GEN_SLEEP_MILLIS = 50;

    /**
     * Private constructor.
     */
    private Ids() {
    }

    /**
     * Gets current date time string.
     *
     * <p>
     * <b>Note</b>: This method is not safe in cluster environment.
     * </p>
     *
     * @return a time millis string
     */
    public static synchronized String genTimeMillisId() {
        String ret;

        ID_GEN_LOCK.lock();
        try {
            ret = String.valueOf(System.currentTimeMillis());

            try {
                Thread.sleep(ID_GEN_SLEEP_MILLIS);
            } catch (final InterruptedException e) {
                throw new RuntimeException("Generates time millis id fail");
            }
        } finally {
            ID_GEN_LOCK.unlock();
        }

        return ret;
    }
}
